In the following, DVB system and DVB receivers are described as examples, although the use of the invention is not restricted to the DVB system. Digital video broadcasting has been under development, and it is seen to gradually replace the analog broadcasting systems. This is because of its ability to offer new types of services and better quality of service. Digital Video Broadcasting has been under standardisation by European Broadcasting Union (EBU) and European Telecommunications Standards Institute (ETSI) that have created a DVB standard ETS 300 800. In the digital broadcasting system data is transferred in bursts within determined time slots. The modulation is e.g. Orthogonal Frequency Division Multiplex (OFDM) modulation.
With digital video broadcasting it is possible to achieve a good quality data transfer even if the receiver is mobile. Therefore the mobile applications of terrestrial DVB (DVB-T) will be important. However, the mobile DVB receivers should be small-sized and lightweight with small-sized batteries. Also, the available time of operation between charging the batteries should be long. In achieving this, the power consumption of mobile DVB receivers may become a problem.
A typical DVB receiver tuner comprises RF IC's and discrete RF blocks. Most of the tuner IC's are operated with +5 V power supply. If the power supply is provided by a low voltage battery (3.7 V), the supply voltage for RF parts must be generated using a voltage converter. While the transmission of data consists of bursts, it would be possible to turn off the receiver for the period of time between the bursts. This kind of solutions are described in patent documents U.S. Pat. Nos. 5,878,336 and 5,515,364. However, there are certain problems related with applying these solutions in a DVB receiver. Firstly, the period between two consecutive bursts may be short and the tuner cannot be switched off, during the transmission break.
A further problem is related to a certain type of step-up converter. Even if the converter is switched off, the output voltage of the converter does not drop down to zero. The remaining supply voltage appears also in the tuner power supply line and consumes power.